{"id":6466,"date":"2024-04-21T23:20:39","date_gmt":"2024-04-22T06:20:39","guid":{"rendered":"https:\/\/zentut.com\/java-tutorial\/java-var\/"},"modified":"2024-04-21T23:21:03","modified_gmt":"2024-04-22T06:21:03","slug":"java-var","status":"publish","type":"page","link":"https:\/\/www.zentut.com\/java-tutorial\/java-var\/","title":{"rendered":"Java var"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the Java var<\/code> keyword to declare variables and understand how Java infers the type of variables.<\/p>\n\n\n\n

Introduction to the Java var keyword<\/h2>\n\n\n\n

Because Java is a statically typed language, every variable<\/a> in Java is associated with a data type. The data type determines the kind of values that the variable can store.<\/p>\n\n\n\n

It means that when you declare a variable, you need to specify its data type upfront. For example, the following defines a variable count and initializes its value to 0:<\/p>\n\n\n

int<\/span> count = 0<\/span>;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Java 10 introduced a new way to declare a variable using the var keyword. For example, the following declares the count<\/code> variable with type int and initializes its value to 0:<\/p>\n\n\n
var<\/span> count = 0<\/span>;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
But how does Java determine the type of the count<\/code> variable? In this case, Java automatically infers the type of the variable count<\/code> using its initial value. Because the value of the count<\/code> is zero, the count<\/code> variable has the type of int<\/code>.<\/p>\n\n\n\n
Since Java uses the initial value to determine the type of variable, you need to initialize the variables declared with the var<\/code> keyword. The following example is not allowed:<\/p>\n\n\n
var<\/span> count;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
In the following example, Java infers the type of the amount<\/code> variable as double because of its initial value 0.00<\/code>:<\/p>\n\n\n
var<\/span> amount = 0.00<\/span>;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
It’s equivalent to the following:<\/p>\n\n\n
double<\/span> amount = 0.00<\/span>;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
The var keyword also allows you to declare multiple variables at once, each variable declaration is separated by a comma (,<\/code>):<\/p>\n\n\n\n
For the primitive data types, the var<\/code> keyword may not have benefits. But later, when you learn about classes, you’ll see how the var<\/code> keyword makes your code more concise. For example, instead of writing the following code:<\/p>\n\n\n
StringBuilder builder = new<\/span> StringBuilder();<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
you can shorten it down using the var<\/code> keyword:<\/p>\n\n\n
var<\/span> builder = new<\/span> StringBuilder();<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Java var and compound declaration<\/h2>\n\n\n\n
When you use an explicit type, you can define multiple variables using a single statement. For example:<\/p>\n\n\n
double<\/span> amount = 98.95<\/span>,\n       salesTax = 0.08<\/span>;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, we declare two variables amount and salesTax<\/code> with the type double. This variable declaration is also known as a compound declaration<\/strong>. <\/p>\n\n\n\n
Unlike explicit variable declarations, Java doesn’t allow you to declare multiple variables using the var<\/code> keyword in a single statement.<\/p>\n\n\n\n
For example, the following will result in an error: “‘var’ is not allowed in a compound declaration”:<\/p>\n\n\n
var<\/span> amount = 98.95<\/span>,\n    salesTax = 0.08<\/span>;<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
    \n
  • The Java var<\/code> keyword automatically infers the type of a variable using its initial value.<\/li>\n\n\n\n
  • The Java var<\/code> keyword cannot be used in a compound declaration.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
    In this tutorial, you’ll learn how to use the Java var keyword to declare variables and understand how Java infers the type of variables.<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":2190,"menu_order":8,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-6466","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/6466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/comments?post=6466"}],"version-history":[{"count":2,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/6466\/revisions"}],"predecessor-version":[{"id":6468,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/6466\/revisions\/6468"}],"up":[{"embeddable":true,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/2190"}],"wp:attachment":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/media?parent=6466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}